RELIEVING GROUND PRESSURE ON UNDERGROUND WORKINGS

摘要

The earth pressure in the underground working area is effectively alleviated by injecting high-pressure liquid into a weak ground stratum underlying the ore bed being excavated thereby to enlarge the stress envelope formed around the working face. The liquid injection hole is formed as by drill means to extend from the working face or a neighboring gateway through an intermediate layer into the weak stratum preferably at a point outside of the stress envelope initially formed.